Chair back frame



FIG. 1 is a front perspective view of an chair back frame;

FIG. 2 is a front elevation view of the chair back frame of FIG. 1;

FIG. 3 is a rear elevation view of the chair back frame of FIG. 1;

FIG. 4 is a left-side view of the chair back frame of FIG. 1;

FIG. 5 is a right-side view of the chair back frame of FIG. 1;

FIG. 6 is a top plan view of the chair back frame of FIG. 1;

FIG. 7 is a bottom plan view of the chair back frame of FIG. 1; and,

FIG. 8 is an enlarged view of a portion of the chair back frame of FIG.1.

CLAIM The ornamental design for a chair back frame, as shown anddescribed.